What is the limit of a project size?

The only true limit on the size of a SuperCard project is available disk space, but there are some other considerations:

When a project grows to a substantial number of cards (>4000) you may see a performance decrease. This can be countered somewhat with regular compacting, but the best solution may be to redesign the project to break it into separate modular projects. Of course, this can vary widely and is offered as only a very general rule of thumb.